Glass Screens & Widgets Unseen

When the Boeing 747-100 entered service in 1970, its three-person flight crew monitored and interacted with the aircraft and its systems through a massively comprehensive cockpit display system (CDS). Leave aside the 747-100’s shear volume of gauges, switches and buttons, however, and very little about its data presentation would have been unfamiliar to the pilot of a Boeing Model 40, an air mail plane and passenger carrier of the 1920s.

Fast-forward 19 years and Northwest Airlines was first to launch revenue operations with the 747-400, a thoroughly modern revision of the classic “jumbo jet,” with a five-screen electronic flight instrumentation system (EFIS), or “glass” cockpit. Crew interaction still occurred via a myriad of switches and buttons, but the plethora of aircraft systems data, plus navigation and other information, was presented on cathode ray tube (CRT) screens.

Since then, lighter, higher-performing LCDs have largely replaced CRTs and the glass cockpit has become an expected feature of even the single piston-engine general aviation types. As the OEMs have expanded and enhanced their CDS offerings, earlier generations of EFIS cockpits have been modified and upgraded, helping keep aircraft entering the second or third phases of their operational life span on the cusp of the latest technology.

“ARINC 661 ensures that the full CDS interactively behaves with the avionics systems in the same manner, regardless of UA developer and CDS supplier.” Kara Gremillion, software developer, ANSYS

Of course, the avionics and display requirements of a Cessna Skyhawk are very different than those of an Airbus A380, yet essentially similar avionics “talk to” and are controlled via essentially similar cockpit screens. Add to this the complexity of interaction with multiple page and layer choices (depending on the user application selected for display), especially through a touchscreen, and it quickly becomes clear that the interface between screen function and avionics is a critical technology. For example, interfacing between screen function and avionics is a key piece of UPS’ Primus Epic cockpit upgrade of its Airbus A300 fleet.

Standardization was a less important consideration in the early years of EFIS, and suppliers of retrofit CDS have needed not only to adapt their products to multiple standards, but also manage CRT replacement and the change from CRT to LCD, ensuring common functionality between the two technologies.

It’s a challenge with which Thomas Electronics, a Clyde, New York-based specialist in replacement CDS units is very familiar. “We have 60 years’ expertise in the video characteristics of CRTs and their intricate behavior,” said CTO Nelson Mino. “We’ve produced algorithms that mimic this behavior beyond just digitization of analog signals, in an inherently safe way so as not to introduce unnecessary failure conditions. The key to the value proposition of our products is that they are a plug-and-play retrofit solution requiring only the effort it takes to replace an existing unit.”

Thomas’ cockpit CRT experience stretches back over 25 years. “With increasingly integrated systems, the technology and products have become more OEM-centric,” Mino said. “Modular systems with multiple boxes serving specific functions are giving way to a single box with integrated functions, making maintenance and repair by third parties increasingly difficult and more expensive for the operator.”

On the other hand, where new systems are concerned, a degree of interface standardization is occurring though the implementation of industry-standard tools, exemplified by ARINC 661. “As a developer of new functions,” Mino said, “any standardization of features for enhanced functionality is a great plus in providing a design standard to work to and a definition.” He said Thomas employees have been on the board of the Airlines Electronic Engineering Committee (AEEC), which provided input to help build the ARINC 661 standard. Nonetheless, given its work across a quarter century’s worth of cockpit architecture, ARINC 661 remains far from standard for Thomas. Mino said the company “has an extensive library of industry standards and guidelines, which we review when introducing enhancements to our hardware and new product lines.”

What is ARINC 661?

As the senior product manager for systems products at Canonsburg, Pennsylvania-headquartered software developer ANSYS, Kara Gremillion’s responsibilities include SCADE Solutions for ARINC 661 Compliant Systems. She described its as a software tool set that empowers avionics engineers to prototype and design ARINC 661-compliant systems, embedded CDS and user applications (UAs).

“The ARINC 661 standard normalizes the design of interactive CDS and the way the CDS communicates with UAs, including flight management, flight control and flight warning systems,” she said. It uses predefined and standardized graphical widgets, some changeable through pilot interaction via trackball, keyboard, tactile screens, etc. by standardizing the communication protocol at runtime between a UA and the CDS. “ARINC 661 ensures that the full CDS interactively behaves with the avionics systems in the same manner, regardless of UA developer and CDS supplier.”

Thomas Global’s CRT-to-LCD plug-and-play display (TFD-8601).

Photo courtesy of Thomas Global

The widgets to which Gremillion refers are integral to ARINC 661 CDS developers using them to create the graphical user interface (GUI). Their incorporation means there’s no requirement to develop graphics from scratch for new or revised UAs, while anything new created through widget use is to a repeatable standard. A widget might deliver a simple graphical representation or bring detailed data into a display from a source within the avionics, such as mapping .

While ARINC 661 specifies how widgets work, their appearance is down to the developer, so that CDS appearances are variable according to developer or customer preference (and re-workable by modifying widget presentation). Widgets also enable manufacturers to generate a particular look or “feel” for their product lines, and a dedicated look modeling appendix was added in Supplement 5 to standardize this look and feel definition. In its first, 2001 iteration, ARINC 661 included 42 widgets. Each supplement added more. Today’s Supplement 6, or ARINC 661-6, features about 80. Dassault, General Electric, Honeywell, Rockwell Collins and Thales are among key contributors to the ARINC 661 CDS standardization subcommittee, which is actively preparing the Supplement 7.

The standard was first employed on the Airbus A380. The OEM remained faithful to it for the A400M and A350XWB, developing the CDS for both using the ANSYS SCADE product. Boeing’s 787 is another ARINC 661 beneficiary, while in 2011, EMBRAER said it would use SCADE Solutions for ARINC 661 in its future developments.

Alternative Approach

Gulfstream introduces its dramatic new Symmetry Flight Deck on its G500 and G600 models, the former scheduled for initial customer delivery in December. Incorporating 10 touchscreens, Symmetry was not developed with ARINC 661, but using Honeywell’s proprietary ASCB, which Gulfstream Senior Experimental Test Pilot Scott Martin explained “uses ARINC 429 or ARINC 739, depending on which application is in active use,“ and ARINC 665 to communicate with other airframe components.

“There are four large screens, two standby flight displays and four avionics screens at the two pilot stations,” Martin said. “The numbers were chosen to enhance dispatchability should a failure occur and did not appreciably affect the complexity. Most of the displayed information is redundant across the various displays of a given type. Also, the underlying connectivity was similar to previous products.”

He said the primary reason for selecting touchscreens was to ease future upgrades to avionics, UAs and the screens themselves. “We can make it control and display anything we might need,” he said, and inevitably, interface technology plays a huge role. “Humans are built to interact directly with a given object of interest. Interaction with virtual visual devices on an electronic screen requires zero training, but it takes special training to know to push a button a few centimeters above, below, or to the side of text on a screen, which is what we’ve always had to do in the past.

“Now we’re at the point of directly interacting with the control of a system/function,” Martin said. “We’ve defined a small set of touch user interfaces that can accommodate any type of touchscreen interaction and it’s a short process to integrate a new application into the flight deck.”

Gulfstream and Honeywell have forged a unique path with the Symmetry Flight Deck, creating a system optimized in the first instance to the G500/600, demonstrating that the market has space for individual interactive CDS solutions. But the wider industry requirement going forward will undoubtedly be towards a common standard, a position ARINC 661 seems likely to assume.

Achieving Symmetry’s Display Design

The OEM developed the flight deck’s physical layout, then defined the airplane’s mission and avionics tasks required to accomplish it. Next, it developed a menu structure for how pilots access tasks, including phase-of-flight tailored menus, and minimalist touch actions with virtual button types, colors, sizes, shapes and styles. This produced six interaction types that became the TUI and page layouts. The finalized layout and intended interaction response “were converted into avionics requirements for Honeywell to implement.”

The touchscreen detects touch location, compares it to the button or slidebar there and completes needed internal format conversion and simple calculations, he said. The system then displays new information, changes the button state or relays the touch to the intended system or application. The screen changes button state or displays new data (as applicable) immediately, then reverts if no feedback is received from the target system.